Downhole sectional screw motor, mounting fixture thereof and method of oriented assembly of working members of the screw motor using the mounting fixture

ABSTRACT

A downhole motor includes a bearing unit connected to a moving section incorporating successively arranged working members--a stator and a rotor interacting with each other along profile surfaces. The like pairs of the adjacent working members are rigidly connected to each other by means of solid threaded bushings. A mounting fixture includes two mounting elements each made as two bushings interconnected by a coupling, the bushings having their profile surfaces located on the same longitudinal axis. One of the bushings is rigidly connected to the coupling, while the other bushing is mounted with the possibility of moving with respect to the longitudinal axis. A method of assembling the downhole motor is effected with the use of a pre-adjusted mounting fixture and resides in interconnecting the like working members by thread bushings ensuring the arrangement of the profile surfaces of the working members analogously to the profile surface of the single monolithic rotor and stator.

FIELD OF THE INVENTION

The invention relates to drilling equipment and, more particularly, to adownhole sectional screw motor and a method of oriented assembly ofworking members thereof using a mounting fixture.

DESCRIPTION OF THE PRIOR ART

Downhole screw motors are being increasingly employed in the practice ofdrilling wells. They are easy to operate and service and have smalldimensions (M. T. Gusman, D. F. Baldenko et al., "Downhole Screw Motorsfor Drilling Wells", Nedra Publishers, Moscow, (1981)).

The length of working members, namely, stators and rotors of screwdownhole motors is limited due to technological possibilities of theirmanufacture. Therefore, specific values of the torque and pressure dropper unit of the length of the working members or one pitch of theirscrew thread are adequately great.

In the easier drilling conditions involving the flushing of a bottomhole with process water, the screw downhole motors feature highefficiency and fully satisfy the requirements of drill men. However, inmost regions there are used drilling muds with a high content of a solidphase, which substantially decreases the service life of the workingmembers and is the factor limiting the universal use of such motors. InSoviet and foreign practice, downhole screw motors are updated by way ofincreasing the length of the working members (the number of screwpitches) with an eye to diminishing the specific contact loads in thescrew pair and, consequently, extending the service life of the workingmembers. Research is conducted in two directions: a long-termdevelopment of the technology of manufacturing monolithic multi-pitchconstructions of rotors and stators, and the elaboration of methods ofsectionalizing the working members of motors.

Today there are known in the art a number of technical solutionsassociated with the sectionalization of the working members of screwdownhole motors.

There is known a method for assembling a sectional screw downhole motorstructurally made in the form of two or more sections of the workingmembers, each section comprising a rotor and a stator (cf. U.S.S.R.Inventor's Certificate No. 286502, cl. F04 5/00, 1969).

The sections are connected in the following manner: the stators areconnected by means of a threaded bushing and the rotors with the aid ofan articulated joint. In the given technical solution the screw surfacesof the connected and like working members may coincide onlyaccidentally. In case of an arbitrary assembly of the working members,when a radial displacement of the adjacent rotors about the axis of thestators is possible in an opposite direction, the operation of the motorfeatures higher radial vibrations because the displacement of thelongitudinal axes of the adjacent rotors may be increased to a doubleeccentricity of the axis of the rotor, relative to that of the stator ina single-section variant of the motor, which leads to the destruction ofthe threaded joints and possible serious failures in the well, as wellas brings about an intensive wear of the contact surfaces of the screwpair due to higher dynamic loads during the motor operation.

There is known in the art a mounting fixture which serves to ensure anoriented assembly of the working members of the screw downhole motor(cf. U.S. Pat. No. 3,982,858, cl. 418-48, 1976).

The fixture comprises a mounting stator and rotor, each beingsufficiently long to accommodate on its profile surface the like workingmembers (stators or rotors) being connected to each other.

The mounting stator or rotor has a profile surface adequate to theprofile surface of the working members being connected.

The method of assembling the motor resides in that it is the section ofthe spindle that is assembled first which comprises bearing and packingunits. Then the working members of the moving sections are successivelyassembled, seeing to it that the profile surfaces are oriented in adesired manner. The sequence of oriented assembly is as follows. Twostators, having similar geometrical dimensions of profile surfaces, areinstalled on the mounting rotor until the end faces having cylindricalsurfaces (external on the first stator and internal - on the second one)contact each other. After ensuring the contact of the end faces, as thestators are fitted on the mated cylindrical surfaces, gage marks areapplied on each stator which provide for a mutual arrangement of thestators with the mounting rotor installed therein. Thus, the profilesurface is continued from one stator to another. Thereafter, themounting rotor is removed, the applied gage marks are checked forcoincidence and both stators are welded to each other along the entireperimeter of the external surface. All the subsequent stators areconnected in an analogous manner.

The rotors of the above motors, ensuring the operation of the motor asthey are installed in the stators, are connected to each other inside asingle mounting stator whose inner surface fully corresponds to theprofile surface of the rotors being connected. Once installed, therotors are secured axially, the mounting stator is removed freeing thejoint between the rotors being connected. Both rotors are weldedtogether along the entire perimeter of the external surface. Thesubsequent rotors are connected in the same manner.

The aforementioned method of oriented connection of the working membersallows the assembly of a requisite amount of the pairs "stator-rotor",the profile surfaces of respective working members being a single screwthread throughout the entire length thereof. Following the installationof the assembled rotors in the assembled stators, the moving section isconnected to the previously assembled spindle section.

A disadvantage of the aforelisted methods of assembling the workingmembers of the motor is technical complexities during the orientedassembly of the working members. The availability of a simplifiedmounting fixture made the motor design more complex. At the same timethe very process of oriented assembly has become more complicated.Besides, welding of the working members is unreliable coupling inarticles operating under stressed conditions of higher loads andvibrations, because the connection of adjacent like working membersinevitably involves skewness and misalignment of their longitudinal axesdue to unparallel location of the end faces of the working members beingsectionalized. The welding of rubber-coated stators may lead to damagingof the rubber lining.

The welded joint makes the motor construction non-detachable and in caseone of the working members of the sections being connected is damaged,there arises the necessity to make a complex repair of the motor orreplace the latter altogether.

Another disadvantage of the said method of assembling the workingmembers is that it is effected without a continuous visual control ofthe mutual arrangement of the screw thread in the rotors and stators ofthe sections being connected, which eventually complicates the assembly.

SUMMARY OF THE INVENTION

It is the principal object of the present invention to provide adownhole sectional screw motor and a method of oriented assembly of itsworking members using a mounting fixture, whereby the welding of theworking members of the downhole motor is dispensed with and its assemblyis streamlined.

This object is accomplished in a downhole sectional screw motor,comprising a bearing unit connected with a moving section incorporatingsuccessively disposed working members and a stator and rotor interactingwith each other along the profile screw surfaces whose start isdetermined by screw threads of these surfaces, the like pairs of theadjacent working members being rigidly axially connected to each other,wherein, according to the invention, the rigid coaxial connection ofeach like pair of the adjacent working member is made in the form of asolid threaded bushing.

The disclosed downhole sectional screw motor whose working members areassembled by means of the solid threaded bushings is more reliable inoperation because the thread bushing compensates for skewness andmisalignment of the axes of the connected working members inevitablyoccurring when joining separately produced working members.

The downhole sectional screw motor in the disclosed assembly ensures amarked increase in the service life of the working members and rules outthe failure of the connection unit thereof.

Besides, this object is accomplished in the mounting fixture fororiented assembly of the working members of the downhole sectional screwmotor, comprising mounting elements with profile surfaces whose start isdetermined by the screw threads of these surfaces which corresponds tothe profile surface of the motor working member, wherein, according tothe invention, the mounting elements are connected in pairs by means ofa coupling and each contains a bushing with a profile surface, one ofsaid bushings is rigidly connected to the coupling, and another ismounted with the possibility of moving relative to its own longitudinalaxis. The said fixture has a disk with an arrester arranged on thecoupling, and the end surfaces of the disk and the movable bushing haveradial cuts equidistant from one another whose number is equal to thatof starts in the profile surface of the mounting element.

The assembly of the disclosed downhole sectional screw motor whoseworking members are connected by the solid thread bushing is possibleonly with the aid of a mounting fixture enabling one to control a mutualarrangement of the screw threads in the adjacent like workingmembers--stators and rotors.

The disclosed mounting fixture ensures a visual control of the qualityof assembly because the bushings linked by a coupling are mounted in theadjacent like working members, and the mutual arrangement of the screwthreads is observed by a relative position of the cuts on the end faceof the movable bushing and the disk.

In the method of adjusting the mounting fixture of the invention, theprofile surfaces of the bushings in the mounting element are superposedwith the profile surface of the adjusting element whose length is notless than the distance between the external end faces of the bushings,and the profile surface is identical to that of the motor workingmember, then, moving the disk with respect to the longitudinal axis ofthe bushings, its radial cuts are superposed with those of the movablebushing, whereupon the disk is rigidly fixed on the coupling by anarrester.

The adjustment of the mounting fixture does not require additionaldevices, and the adjusting element is a conventional element of thescrew pair--a rotor or stator designed for assembling the downholesectional screw motor.

This object is also accomplished owing to the fact that in the method oforiented assembly of the working members of the downhole sectional screwmotor comprising the superposition of the profile surfaces of theworking members of the motor and bushings of the mounting elements inthe mounting fixture, according to the invention, the like workingmembers are connected to each other by thread bushings with apre-fastening along the threaded, the profile surfaces of the bushingsof the mounting elements of the adjusted mounting fixture are superposedrespectively with the profile surfaces of the working members beingconnected and the threads are finally fixed in the range of angulardisplacement of the working members, being connected within the limitsof permissible torques on the screwed threads until the radial cuts onthe disk coincide with those on the movable bushing of the mountingelement.

The method of assembling the downhole sectional screw motor using apre-adjusted mounting fixture streamlines the technological process ofassembly, because the application of the mounting fixture rules outadditional technological operations and ensures necessary accuracy oforienting the screw threads in the adjacent like working members.

Other objects and advantages of the present invention will become moreapparent from the following detailed description of the exemplaryembodiments thereof, with reference to the accompanying drawings inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a downhole sectional screw motor, longitudinal section;

FIG. 2 is a mounting fixture for oriented assembly of rotors in thedownhole sectional screw motor, longitudinal section;

FIG. 3 is a correcting device of the mounting fixture for assemblingrotors (a view taken along arrow B of FIG. 2);

FIG. 4 is a mounting fixture for oriented assembly of stators in thedownhole sectional screw motor, longitudinal section;

FIG. 5 is a correcting device of the mounting fixture for assemblingstators (a view taken along arrow B of FIG. 4).

FIG. 6 is a diagram illustrating the method of adjusting the mountingfixture for oriented assembly of rotors;

FIG. 7 is a diagram illustrating the method of adjusting the mountingfixture for oriented assembly of stators.

FIG. 8 is a diagram illustrating the method of oriented assembly of therotors in the downhole sectional screw motor;

FIG. 9 is a diagram illustrating the method of oriented assembly of thestators in the downhole sectional screw motor.

DESCRIPTION OF THE EMBODIMENTS

The downhole sectional screw motor, as it is represented in FIG. 1,comprises moving sections 1 and 2, as well as a spindle section 3. Eachmoving section 1 (2) contains working members--a stator 4 (5) and arotor 6 (7) arranged thereinside. The stator 4 (5) is a metal body 8 (9)which an elastic lining 10 (11) is vulcanized to. The part of theelastic lining 10 (11) of the stator 4 (5) which contacts the rotor 6(7) has a multiple-start screw profile surface 12 (13).

The rotor 6 (7) has an outer multiple-start screw profile surface 14(15) contacting with a mated profile surface 12 (13) of the elasticlining 10 (11) of the stator 4 (5). The amount of starts of the profilesurface 14 (15) of the rotor 6 (7) differs by one from the amount ofstarts of the profile surface 12 (13) of the elastic lining 10 (11) ofthe stator 4 (5).

The rotor 6 (7) is arranged inside the stator 4 (5) so that its axis islocated away from the axis of the stator 4 (5) to the value ofeccentricity "e".

As the profile surfaces 12 (13) of the elastic lining 10 (11) of thestator 4 (5) and rotor 6 (7) contact with each other, they form chambersC for the passage of fluid or other working agent.

The stators 4 and 5 of the moving sections 1 and 2 are connected to eachother via a solid threaded bushing 16. Also secured to an upper stator 4with the aid of a threaded is a thread bushing 17 through which themotor is connected to a drill pipe string (not shown in the FIG.) Thelower stator 5 of the moving section 2 is connected to a body 18 of thespindle section 3 by means of the thread.

The rotors 6 and 7 are also connected to each other by means of a solidthreaded bushing 19.

The use of solid threaded bushings 16 and 19 to connect the stators 4and 5 and rotors 6 and 7, respectively, makes it possible to coaxiallylink the stators 4 and 5 and to coaxially link the rotors 6 and 7.

In its lower part the rotor 7 of the moving section 2 is connected to anoutput shaft 20 of the spindle section 3 which, in turn, is connected toa rock destruction tool (not shown in the FIG.)

A mounting fixture 21 (FIG. 2) for oriented assembly of the rotors 6 and7 of the downhole sectional screw motor comprises two mounting elements22 and 23 linked to each other with couplings 24. The mounting element22 is a bushing 25 to the inner surface of which in the given variant ofembodiment an elastic lining 26 having a multiple-start screw profilesurface 27 vulcanized thereto. The amount of starts in the profilesurface 27 is equal to the amount of starts in the profile surface 14(15) of the rotors 6 (7), and the profile of the surface 27 is made sothat as it is mated with the profile surface 14 (15) of the rotors 6 (7)so there is no clearance between them.

The mounting element 23 is made in the form of a body 28 accommodating abearing 29 secured by a pin 30. The body 28 is rigidly connected to thebushing 25 by means of the couplings 24. Mounted in the bearing 29 is amovable bushing 31. In the given variant of an embodiment the mobilityof the bushing 31 is ensured by the possibility of its rotation aboutits longitudinal axis. The bushings 25 and 31 are mounted coaxially.

A stop ring 32 is mounted on the outer surface of the bushing 31 toprevent the latter's axial movement.

Like the bushing 25, the movable bushing 31 has an elastic lining 33vulcanized to its inner surface. This lining has a multiple-start screwprofile surface 34. The number of starts in the surface 34 and themaking of the profile are analogous to the profile surface 27 of theelastic lining 26 of the bushing 25.

The mounting fixture described herein is furnished with a correctingdevice 35 incorporating a disk 36 (FIG. 2,3) secured on the body 28 withthe aid of a screw 37. Cuts 38 and 39 are applied on the end face of thedisk 35 and the bushing 31, respectively. The distances between the cuts38 on the surface of the disk 36 are determined by the value of centralangle α and are the same and equal between any two adjacent cuts 38.Also equidistant from each other are cuts 39 on the end face surface ofthe bushing 31.

The number of the radial cuts 38 and 39 on the disk 36 and bushing 31 isequal to the number of starts on the screw profile surface 14 (15) ofthe rotors 6 (7).

The coupling 24 rigidly connecting the mounting elements 22 and 23 hasthreaded ends with nuts 40 which help regulate the distance between themounting elements 22 and 23 in an axial direction.

A mounting fixture 41 for oriented assembly of the stators 4 and 5 ofthe downhole sectional screw motor (FIG. 4) is made similarly.

The mounting fixture 41 described herein consists of two mountingelements 42 and 43. The mounting element 42 is a bushing 44 with amultiple-start screw profile surface 45. The bushing 44 is rigidlyconnected to a coupling 46 which also accommodates a mounting element43. Arranged between the coupling 46 and the mounting element 43 is abearing 47 which in the given variant of an embodiment of the mountingfixture 41 allows the rotation of the mounting element 43 about thelongitudinal axis of the bushing 44. To preclude an axial movement ofthe mounting element 43 along the coupling 46, the latter accommodates astop ring 48. The mounting element 43 is made in the form of a movablebushing 49 with a multiple-start screw profile surface 50. Bushings 44and 49 are mounted coaxially.

Like the previous one, the mounting fixture 41 described herein isfurnished with a correcting device 51 (FIG. 4,5) which comprises a disk52 arranged on a tapered surface 53 of the coupling 46. To rigidlysecure the disk 52, provision is made for a nut 54 which can axiallymove along the coupling 46 in the thread.

Arranged on the end face surface of the disk 52 are radial cuts 55. Thedistances between the cuts 55 are determined by the value of centralangle β and are the same and equal between any two adjacent cuts 55.Also equidistant from each other are cuts 56 on the end face surface ofthe movable bushing 49.

The number of radial cuts 55 and 56 on the disk 52 and bushing 49 isequal to the number of starts on the screw profile surface 12 (13) ofthe elastic lining 10 (11) of the stator 4 (5). In turn, the profiles ofthe surfaces 45 and 50 of the bushings 44 and 49, respectively, are madeso that when they mate with the profile surface 12 (13) of the elasticlining 10 (11) of the stator 4 (5), there is no clearance therebetween.

The adjustment of the mounting fixture 21 or of mounting fixture 41 fororiented assembly of the rotors 6 and 7 (or stators 4 and 5) of thedownhole sectional screw motor is performed so that a single profilesurface of the mounting elements 22 and 23 (42 and 43) is preserved,while the latter are arranged on the profile surfaces 14 and 15 (12 and13) of the connected rotors 6 and 7 (or stators 4 and 5) with thepossibility of carrying out continuous visual control, i.e., the profilesurface 34 (50) of the mounting element 23 (43) is the continuation ofthe profile surface 27 (45) of the mounting element 22 (42).

A method of adjusting the mounting fixture 21 for oriented assembly ofthe rotors 6 and 7 resides in the following (FIG. 6): the mountingfixture 21 is arranged on the profile surface 57 of an adjusting rotor58. Length L₁ of the multiple-start profile surface 57 of the rotor 58is at least equal to distance L₂ between outer end faces 59 and 60 ofthe mounting elements 22 and 23. Since the profile surfaces 27 and 34 ofthe elastic linings 26 and 33 of the mounting elements 22 and 23 areadequate to the profile surface 57 of the adjusting rotor 58, once themounting fixture is installed on the adjusting rotor 58, in thisposition the profile surface 34 of the lining 33 of the mounting element23 will be the continuation of the profile surface 27 of the elasticlining 26 of the mounting element 22. At the same time, the mountingelements 22 and 23 are rigidly linked with each other by couplings 24,and the disk 36 of the correcting device 35 is in a free, unfixedposition. Rotating the disk 36 about the longitudinal axis of thebushings 25, 31, the disk 36 is displaced in an angular direction sothat the radial cuts 38 of the disk 36 coincide with the radial cuts 39applied on the end face surface of the bushing 31. Since the radial cuts38 and 39 on both parts are applied uniformly, i.e., the central angle αbetween any two adjacent radial cuts is the same, the radial cuts 38 and39 may coincide at any position of the disk 36. After the disk 36 isinstalled relative to the bushing 31 so that the cuts 38 coincide withthe cuts 39, without changing the position of the parts, the position ofthe disk 36 is fixed with respect to the body 28 with the aid of a screw37. Because the body 28 of the mounting element 23 is rigidly connectedto the bushing 25 of the mounting element 22 by means of the coupling24, and the disk 36 is rigidly secured relative to the body 28, themounting fixture 21 is on the profile surface 57 of the adjusting rotor58, and the fixture 21 is considered to be adjusted upon the completionof these operations.

The mounting fixture 41 for oriented assembly of the stators 4 and 5(FIG. 7) is adjusted in a similar manner. The adjustment techniqueconsists in the following. The mounting fixture 41 is arranged on theprofile surface 61 of the adjusting stator 62. In the given variant ofan embodiment the adjusting stator 62 is made in the form of a body 63with an elastic lining 64 vulcanized to its inner surface. Length L₃ ofthe profile surface 61 of the adjusting stator 62 is at least equal to arespective distance L₄ between the outer end faces 65 and 66 of themounting elements 42 and 43. Like in the preceding case, the profilesurface 61 of the elastic lining 64 of the adjusting stator 62 isadequate to the profile surfaces 45 and 50 of the mounting elements 42and 43. Therefore, after installing the mounting fixture 41 in theadjusting stator 62 the profile surface 50 of the mounting element 43will be the continuation of the profile surface 45 of the mountingelement 42.

The bushing 44 of the mounting element 42 is rigidly secured on thecoupling 46, and the position of the movable bushing 49 is conditionedby the adjusting stator 62 inside of which there is the mounting fixture41. The disk 52 rotates about the longitudinal axis of the bushings 44,49 in an angular direction so that the radial cuts 55 of the disk 52coincide with the radial cuts 56 on the end face surface of the movablebushing 49. Whereupon, the disk 52 is moved axially to the taperedsurface 53 of the coupling 46 with the aid of a nut 54 and said disk 52is secured on the latter. Because once the bushing 44 of the mountingelement 42 and the disk 52 of the correcting device 51 of the mountingelement 43 have been arranged on the profile surface 61 of the adjustingstator 62, and the cuts 55 and 56 of the disk 52 and the movable bushing49 have been rigidly secured on the coupling 46, the adjustment of themounting fixture is considered to be completed.

The thus adjusted mounting fixtures 21 and 41 are further used fororiented assembly of the stators 4 and 5 and rotors 6 and 7 of thedownhole sectional screw motor.

The assembly of the downhole sectional screw motor is performed by asuccessive assembly of the rotors 6 and 7 and the stators 4 and 5 of themoving sections 1 and 2. The rotors 6 and 7 are assembled in thefollowing manner (FIG. 8). The rotors 6 and 7 are connected to eachother by means of the threaded bushing 19, whereupon, they arepre-secured along the threads 67 and 68. Then, the mounting fixture 21with the correcting device 35 is arranged on the profile surfaces 14 and15 of the rotors 6 and 7 the parts being connected in such a manner thatthe profile surface 27 of the elastic lining 26 of the mounting element22 is located on the profile surface 14 of the rotor 6, while theprofile surface 34 of the elastic lining 33 of the movable bushing 31 ofthe mounting element 23 is located on the profile surface 15 of therotor 7. Thereafter, threads 67 and 68 are finally secured. As thethreads 67 and 68 are secured, the rotor 6 is fixed immovably along withthe mounting element 22 of the mounting fixture 21, which is alsorigidly fixed. The rotor 7 installed in the movable portion of amechanical assembly wrench (not shown in the Fig.) rotates along withthe movable bushing 31 relative to the immovable body 28 of the mountingelement 23. As the threads 67 and 68 are screwed, there is attained thecoincidence of the radial cuts 39 of the movable bushing 31 with theradial cuts 38 of the disk 36 of the pre-adjusted correcting device 35in the range of angular displacement of the parts being connected(rotors 6 and 7 and thread bushing 19) within the limits of permissibletorques on the screwed threads 67 and 68. During the assembly there iseffected a constant visual control of the value of screwing torque andthe position of the radial cuts 38 and 39.

The rotors 6 and 7 assembled in such a manner have the profile surfaces14 and 15, one being the continuation of the other, or in other words,are a monolithic rotor with a single profile surface.

The oriented assembly of the stators 4 and 5 of the downhole sectionalmotor is performed in a similar manner with the aid of the mountingfixture 41 with the correcting device 51 (FIG. 9). At first, the stators4 and 5 are connected to each other by means of the threaded bushing 16and all the connected parts are pre-secured to each other along thethreads 69 and 70. Then, the mounting fixture 41 with the correctingdevice 51 are arranged on the profile surfaces 12 and 13 of the stators4 and 5 so that the profile surface 45 of the bushing 44 of the mountingelement 42 is on the profile surface 12 of the elastic lining 10 of thestator 4, and the profile surface 50 of the movable bushing 49 of themounting element 43 is on the profile surface 13 of the elastic lining11 of the stator 5. Then the threads 69 and 70 are finally secured. Asthe threads 69 and 70 are secured, the stator 4 is rigidly fixedalongside the mounting element 42 of the mounting fixture 41 which isalso fixed, and the stator 5 with the movable bushing 49 of the mountingelement 43 rotates in the movable portion of the mechanical wrench (notshown in the Fig.) with respect to the immovable disk 52 rigidly securedon the coupling 46. The coincidence of the radial cuts 56 of the movablebushing 49 with the radial cuts 55 of the disk 52 of the correctingdevice 51 is attained in the range of angular displacements of the partsbeing connected (the stators 4 and 5 and the threaded bushing 16) withinthe limits of permissible torques on screwed threads 69 and 70.

Like in the case of the oriented assembly of the rotors 6 and 7, thestators 4 and 5 assembled according and 13 anzaloguus to the profilesurface of the single monolithic stator.

A requisite amount of the like parts (rotors and stators) can beassembled into a single monolithic group having a single profilesurface. Then, the rotors 6 and 7 assembled in such a manner areinstalled in the stators 4 and 5 assembled analogously, the threadedbushing 17 is secured to the upper stator 4 and both moving sections 1and 2 are connected with the spindle section 3 of the screw downholesectional motor (FIG. 1).

INDUSTRIAL APPLICABILITY

The present invention can be most advantageously used as a hydraulicdownhole motor for drilling oil and gas wells.

The invention can also be used in the mining industry, in drillingartesian, geological-exploratory wells and the overhaul of wells.

We claim:
 1. A method of oriented assembly of successive working membersof a downhole sectional screw motor which includes an output shaft, amoving section connected to the output shaft and incorporatingsuccessively arranged working members each working member including astator and a rotor each having screw surfaces that interact with eachother and having multiple screw starts that are equal for pairs of thesurfaces, the like pairs of the adjacent working members being rigidlycoaxially connected to each other, wherein the rigid coaxial connectionof each like pair of the adjacent working members is made in the form ofa solid threaded bushing using a frame including mounting elements eachhaving multiple start screw profile surfaces, the number of multiplestarts being equal and determined by the number of starts of screwthreads on a screw profile surface of a working member of the motor,coupling means for connecting the mounting elements in spacedrelationship, a bushing carried in each mounting element and having asurface defining the screw profile surface, the bushings being installedcoaxially with each other, one of the bushings being rigidly connectedto the coupling means and the other bushing mounted for movement withrespect to its longitudinal axis, a disk including securing means, thedisc carried by one mounting element of the coupling the disk and themovable bushing each having angularly equidistantly spaced radial cutswhose number is equal to the number of starts in the profile surfaces ofthe mounting elements, which method comprises: superposing the profilesurfaces of the working members of the motor and the bushings of themounting elements of the mounting fixture, connecting like workingmembers to each other by threaded bushings with a pre-securing movementalong the threads superposing the profile surfaces of the bushings ofthe mounting elements of the adjusted mounting fixture respectively withthe profile surfaces of the working members being connected, andsecuring the threads in the range of angular displacements of theconnected working member within the limits of the permissible torques onthe screwed threads until radial cuts on the disk and radial cuts on themovable bushing of the mounting element are aligned.
 2. A method ofadjusting a mounting fixture for oriented assembly of successive workingmembers of a downhole sectional screw motor, wherein said mountingfixture includes a frame having mounting elements each having multiplestart screw profile surfaces, the number of multiple starts being equaland determined by the number of starts of screw threads on a screwprofile surface of a working member of the motor, coupling means forconnecting the mounting elements in spaced relationship, a bushingcarried in each mounting element and having a surface defining the screwprofile surface, the bushings being installed coaxially with each other,one of the bushings being rigidly connected to the coupling means andthe other bushing mounted for movement with respect to its longitudinalaxis, a disk including securing means, the disc carried by one mountingelement of the coupling the disk and the movable bushing each havingangularly equidistantly spaced radial cuts whose number is equal to thenumber of starts in the profile surfaces of the mounting elements, saidmethod comprising; superposing the profile surfaces of the bushings ofthe mounting elements with the profile surface of an adjusting elementwhose length is not less than the distance between external end faces ofthe bushings and the profile surface of the adjusting element isidentical to that of the working member of the motor, and moving a diskrelative to the longitudinal axis of the bushings until radial cuts inthe disc are aligned with radial cuts in the movable bushing and rigidlysecuring the disk on the coupling by means of an arrester.
 3. A mountingfixture for oriented assembly of successive working members of adownhole sectional screw motor which includes an output shaft, a movingsection connected to the output shaft and incorporating successivelyarranged working members each working member including a stator and arotor each having screw surfaces that interact with each other andhaving multiple screw starts that are equal for pairs of the surfaces,the like pairs of the adjacent working members being rigidly coaxiallyconnected to each other, wherein the rigid coaxial connection of eachlike pair of the adjacent working members is made in the form of a solidthreaded bushing, said fixture comprising: mounting elements each havingmultiple start screw profile surfaces, the number of multiple startsbeing equal and determined by the number of starts of screw threads on ascrew profile surface of a working member of the motor, coupling meansfor connecting the mounting elements in spaced relationship, a bushingcarried in each mounting element and having a surface defining the screwprofile surface, the bushings being installed coaxially with each other,one of the bushings being rigidly connected to the coupling means andthe other bushing mounted for movement with respect to its longitudinalaxis, a disk including securing means, the disc carried by one mountingelement of the coupling, the disk and the movable bushing each havingangularly equidistantly spaced radial cuts whose number is equal to thenumber of starts in the profile surfaces of the mounting elements.